1) Field of the Disclosure
The disclosure relates to thermal management systems and methods. In particular, the disclosure relates to chemical reaction-based thermal management systems and methods.
2) Description of Related Art
Various components in aircraft, satellites, and other vehicles and craft may generate heat and require cooling. For example, without limitation, line replaceable units and other components in an aircraft or satellite network may require cooling to maintain those components at an appropriate operating temperature. These types of components may generate heat constantly. Other components may generate heat on a non-constant basis. These types of components may generate heat based on an event that may be periodic or non-periodic. For example, without limitation, directed energy weapons, such as lasers or high power microwave systems, that may be carried as a payload may generate heat when those weapons are used. The heat generated may be a large amount of heat over a short period of time. With these and other systems, it may be desirable to provide required cooling for a lowest possible weight.
Lightweight thermal management of heat sources is needed for energy-consuming payloads on mobile platforms, such as aircraft and satellites, particularly where the payload has extremely high cooling loads, such as hundreds of kilowatts, for relatively brief periods of time, such as seconds or minutes. Such payloads may include, without limitation, directed energy weapons such as lasers or high power microwave systems and radar systems. Known thermal management systems exist. One known system uses coolers that exchange heat with ambient air for direct heat rejection. However, such direct heat rejection systems may use large quantities of ram air, which is air outside of the aircraft, and performance may be dependent on ambient temperature, thus restricting the operational envelope. The operational envelope may include speed, altitude, and ambient external conditions such as weather. Another known system uses coolers, refrigerators, or chilling devices that use working fluids in a closed cycle for overboard heat rejection from a low-temperature heat sink to a high-temperature heat sink. However, such closed cycle refrigeration systems may be ill-suited to direct management of thermal loads owing to power, weight, and slow transient response. Another known system uses thermal mass to absorb the heat or sensible heat. For purposes of this application, sensible heat is defined as potential energy in the form of thermal energy or temperature. However, such thermal mass for sensible heat systems may provide limited thermal capacity over a relatively small temperature range due to the low heat capacity of applicable materials. Specific mass, that is, heat per unit mass, is typically not high and systems can quickly become mass-intensive as thermal storage requirement increases. Another known system involves the use of latent heat. Latent heat of phase transitions such as melting (solid to liquid), boiling (liquid to gas), and sublimation (solid to gas) are capable of absorbing heat over a relatively narrow temperature range, which is advantageous for directed energy weapons such as lasers. Phase change materials may either remain on the platform or may be rejected overboard.
Known approaches for using endothermic reactions to provide thermal capacity for heat loads may entail the progressive conversion of a supply of reactants into products. This relies on the thermally-driven equilibrium and kinetics between reactants and products in which the equilibrium composition shifts as the temperature is changed. This may result in a temperature limit on the extent to which the reactants can be converted to products, which in turn, can limit the amount of heat that can be absorbed per unit of mass of reactant. The reactant and product mix may be undifferentiated, thus maintaining the same overall stoichiometry as the reaction progresses from reactants to products. For either a recirculating or once-through reaction mixture flow scheme, accumulation of product can limit the reaction conversion and consequently limit obtainable specific weight.
Accordingly, there is a need for a chemical reaction-based thermal management system and method that provides advantages over known systems and methods.